The Future Will Be Quiet

U.S. cities can be very loud places. Between the sounds of car horns, sirens, truck traffic, and people yelling, background-noise levels can regularly reach 70 decibels—about as loud as the drone of a vacuum cleaner at close range. That much noise pollution isn’t just annoying; it can heighten stress, disrupt your sleep, and even lead to heart disease. Researchers at the University of Michigan estimate that about one-third of Americans are exposed to harmful noise, and might be at risk of noise-related health problems.

While countries in Europe have enforced stringent national noise standards, Americans have for the most part just made more noise; last year, more than 340,000 noise complaints were filed in New York City alone. But there are signs that people in the U.S. are getting serious about the problem, and new technologies can help. Here’s how the cities and suburbs of the future could become quieter, more peaceful places.

1. Cars That Don’t Go Vroom

Because electric engines are all but silent, the push for greater fuel efficiency could mean not just cleaner air but quieter streets. If electric cars become more popular (or are mandated by the government), “the whole soundscape of our cities would change rapidly,” Holger Schulze, a musicology professor and the principal investigator at the Sound Studies Lab at the University of Copenhagen, told me. Car horns and sirens could be made quieter, too, because they wouldn’t have to drown out revving engines. Noises like bicycle bells and people’s voices might become the dominant sounds of a city.

Governments and businesses are already switching to electric fleets. Jim Castelaz, the founder and CEO of Motiv, a California company that manufactures power trains for large electric vehicles, told me that parents now sometimes ask drivers of electric school buses to honk when dropping children off, because they can’t hear the buses coming. (Electric and hybrid vehicles may actually be too quiet; the National Highway Traffic Safety Administration is working on new rules that will require such vehicles to make a minimum amount of noise at low speeds so that pedestrians can hear them coming.)

Even electric vehicles still make noise when they’re speeding along the pavement, of course. But Arizona, California, and other states have begun experimenting with something called quiet pavement, a rubberized asphalt or smooth concrete mix designed to lessen sound. In Phoenix, it cut traffic noise by 6 to 12 decibels, according to Robert Bernhard, the vice president for research at the University of Notre Dame.

2. A Truce on Leaf Blowers

People across the United States have been fighting for years to ban leaf blowers, which are not only loud but also dirty. (As Atlantic national correspondent and noted leaf-blower opponent James Fallows has pointed out, gas-powered leaf blowers with cheap two-stroke engines can spew as much pollution in half an hour as a Ford F-150 pickup does driving across the U.S. one and a half times.) The issue has proved contentious, at times pitting neighbor against neighbor. But technology offers a compromise.

The demand for long-lasting laptops and mobile phones has spurred innovations in batteries, which can now power some of the noisiest devices, including leaf blowers and lawn mowers—making them far cleaner and quieter. Even jackhammers can be made quieter: In 2014, construction crews in New York City started using electric jackhammers, which are reportedly about half as loud as traditional ones.

3. Targeted Sirens

When a fire truck screams down a city street, thousands of people might hear it, even if only a couple dozen need to get out of the way. In a few decades, though, emergency vehicles might send sirens directly to cars’ Internet-connected audio systems and to the phones and smartwatches of pedestrians nearby, Schulze, of the Sound Studies Lab, told me. Emergency signals could be marked high priority, so as to interrupt music or phone calls, he said.

Self-driving cars could virtually eliminate the need for sirens and horns, Raj Patel, the global leader of acoustics at Arup, a design firm, told me. Already, the cars are programmed to drive more conservatively if they detect flashing lights, and in the future, emergency alerts could be sent directly—and silently—to their computer systems. We would still need a way to alert pedestrians and bicyclists, however.

Sirens may one day be directed so that only people in an emergency vehicle’s path have to hear them. Museums already use directional sound to enable patrons to hear audio from one exhibit without disturbing other visitors nearby. Significant technical hurdles would have to be overcome to achieve similar results with sirens, but a British company called Directional Sirens is marketing prototypes that focus the siren’s sound horizontally, so that people in high-rise buildings won’t hear it as much. Perhaps in the future, directional-noise technology could be made to work for horns, too, so that drivers (or self-driving cars) could point a focused beam of sound at the one person in their way and spare everyone else.

4. Stealthy Airplanes

According to the Federal Aviation Administration, the number of Americans affected by significant aircraft noise fell by 95 percent from 1970 to 2004, even as the number of flights increased. Satellite systems have made it possible for planes to take off and land at much steeper angles, and some researchers think this has reduced the noise that reaches communities. More important, airplane engines have become much quieter. The Airbus A380, known as the quietest plane of its size, produces about half as much noise as a 747 upon takeoff and one-quarter as much upon landing, according to Airbus.

Engineers working on NASA’s Environmentally Responsible Aviation Project are designing airplanes that would be even quieter. One design has airplanes running on hybrid engines; another puts the engines above the wings rather than below them, to minimize the noise heard on the ground. NASA hopes that by 2025, the most-advanced aircraft will be half as loud as they are now.

5. Better Noise Control

Even as technology helps us quiet today’s worst noises, it may introduce new sounds to take their place. If more packages are delivered by drones, for example, the rumble of delivery trucks could be replaced by a whirring overhead. Advertisers in loud cities such as New York and Chicago have used directional sound to send audio messages to individuals walking by a billboard or store display; as more advertisers struggle to reach people through TV and the Internet, will they assault us with audio ads whenever we step outside?

Thankfully, devices to block sound are also becoming more sophisticated. Active noise control, a technology used in high-end noise-canceling headphones, sends out a sound wave that has the opposite wavelength of the incoming noise, thus canceling it out. Today’s active-noise-control devices are good at blocking constant ambient noise but less effective against sudden sounds—dogs barking or cars backfiring. Advances in computing could change this, Patel said. Engineers are working to improve noise-canceling devices that detect abrupt sounds through microphones and then quickly send out a signal to neutralize them.

Brigitte Schulte-Fortkamp, a professor of psychoacoustics and noise effects at the Technical University of Berlin, has pioneered ways to allow people to hear nature sounds even in the middle of a city. In one small Berlin park where noise levels surpassed 60 decibels, she and her team installed a sound-absorbing wall and devices on benches that projected birdsong, creating a more pleasant setting.

Technology might also make it easier to target noise scofflaws. Already, phone apps can estimate how much sound a car or truck makes. Perhaps one day, Notre Dame’s Bernhard says, we’ll have devices similar to red-light cameras that can catch a passing vehicle emitting a noise louder than the legal limit, take a picture of that vehicle’s license plate, and send the driver a ticket. And who knows? Maybe technology will even be able to locate the noisy leaf blowers still out there and, with a little technical interference, cause them to (silently) self-destruct.

A Brief Chronicle of Noise

Beginning of time: Despite its name, the Big Bang is silent, because there is no existing space through which sound waves can travel.

Circa 1800: John Robison, a Scottish scientist, invents a precursor to the siren. He intends it as a musical instrument.

1883: A volcano erupts in Indonesia, producing what may be the loudest sound ever recorded. It is heard 3,000 miles away.

1913: A prisoner in Denver invents an early version of the car alarm.

1986: Bose produces the first noise-reduction headset, for pilots on a record-breaking around-the-world flight.

2006: Police departments nationwide phase in car sirens that make nearby objects shake, to alert people listening to loud music.

2020: Sound-wave guns that emit “sonic bullets”—focused beams of noise that give the target an instant migraine—become the weapon of choice for police officers.

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